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van der Poel, Erwin P.; Verzicco, Roberto; Grossmann, Siegfried; Lohse, Detlef

Plume emission statistics in turbulent Rayleigh–Bénard convection

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  • Media type: E-Article
  • Title: Plume emission statistics in turbulent Rayleigh–Bénard convection
  • Contributor: van der Poel, Erwin P.; Verzicco, Roberto; Grossmann, Siegfried; Lohse, Detlef
  • imprint: Cambridge University Press (CUP), 2015
  • Published in: Journal of Fluid Mechanics
  • Language: English
  • DOI: 10.1017/jfm.2015.176
  • ISSN: 0022-1120; 1469-7645
  • Origination:
  • Footnote:
  • Description: <jats:p>Direct numerical simulations (DNS) of turbulent thermal convection in a <jats:inline-formula><jats:alternatives><jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" xlink:type="simple" xlink:href="S0022112015001767_inline1" /><jats:tex-math>$\mathit{Pr}=0.7$</jats:tex-math></jats:alternatives></jats:inline-formula> fluid up to <jats:inline-formula><jats:alternatives><jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" xlink:type="simple" xlink:href="S0022112015001767_inline2" /><jats:tex-math>$\mathit{Ra}=10^{12}$</jats:tex-math></jats:alternatives></jats:inline-formula> are used to study the statistics of thermal plumes. At various vertical locations in a cylindrical set-up with aspect ratio <jats:inline-formula><jats:alternatives><jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" xlink:type="simple" xlink:href="S0022112015001767_inline3" /><jats:tex-math>${\it\Gamma}=\text{width}/\text{height}=1/3$</jats:tex-math></jats:alternatives></jats:inline-formula>, plumes are identified and their properties extracted. It is found that plumes are much less likely to be emitted from plate regions with large wind shear. Close to the plates, the plumes have a unimodal log–normal distribution, whereas at more central locations the distribution becomes weakly bimodal, which can be traced back to clustering of the plumes and influence of the large-scale circulation. The number of hot plumes decreases with height. The width of the plumes scales with <jats:inline-formula><jats:alternatives><jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" xlink:type="simple" xlink:href="S0022112015001767_inline4" /><jats:tex-math>$\mathit{Ra}$</jats:tex-math></jats:alternatives></jats:inline-formula> approximately as <jats:inline-formula><jats:alternatives><jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="gif" xlink:type="simple" xlink:href="S0022112015001767_inline5" /><jats:tex-math>$\mathit{Nu}^{-1}$</jats:tex-math></jats:alternatives></jats:inline-formula>, indicating that it is determined by the thermal boundary layer thickness.</jats:p>